What do lumens provide? Unit of measurement of luminous flux lumen

Luminous flux is light energy emitted by a point source. Since it depends on the distance, it is expressed in spatial angles.

Lumen is a unit of measurement of the power of light radiation, which is estimated by the sensation of light to the human eye.

The unit of measurement for luminous flux, lumens, can be thought of as the total amount of light. For example, a 40 W incandescent lamp will create a luminous flux corresponding to 415 lumens, a fluorescent lamp will create a flux of 3200 lumens. Place any optical system around the light source, the amount of light (lumens) will be the same. Thus, if the number of lumens is not written on a non-directional light source, then it is not clear how it will illuminate.

Illumination and brightness

Illuminance is the amount of light, it quantifies light, which falls on a particular surface area of ​​the body. It depends on the wavelength of light, because the human eye perceives the brightness of different wavelengths of light differently, in other words, different colors.

Illuminance is calculated for different wavelengths separately. People perceive the brightest colors as:

• green - light with a wavelength of 550 nanometers;
• yellow orange. They are located next to it on the spectrum.

The light coming from red, blue and violet colors has a short or long wavelength, so they are perceived as darker. The concept of illumination is often correlated with the concept of brightness.

When lighting an area with the same lamp, a large area will be less illuminated than a small one.

Difference between brightness and illuminance

The Russian language gives two answers to the question of what brightness is. Brightness means a characteristic of luminous bodies, that is, a physical quantity. It also defines a subjective concept that depends on many factors, for example:

• structural features of human eyes;
• amount of light in the room.

The less light there is in the environment, the brighter the light source appears to us. You should distinguish between brightness and illumination and remember the following:

• brightness is the light that is reflected from the surface of a luminous object;
• Illuminance is the light that falls on the illuminated surface.

In astronomy, brightness includes two concepts, where stars emit and planets reflect. In this science, stellar brightness is measured on a photometric scale, and the greater brightness of the star is correlated with a smaller value. The brightest stars have a negative magnitude.

The unit of luminance (candela per square meter) is used for applied or physiological purposes.

The lux unit is used to calculate light levels. One lux is equal to one lumen per square meter. The foot-candle is also used to measure illumination. She is consulted in the fields of cinema and photography and some others. The foot is in the name because the foot-candle means the candela illumination of a square foot of surface, measuring in one foot intervals.

Photometer

A photometer is a device that measures illumination. The light enters the photodetector, then is converted into an electrical signal and measured. There are photometers that operate on a different principle. Mostly photometers show light levels in lux, but there are also those who use other units. Those photometers, also called exposure meters, are involved in determining shutter speed and aperture, thereby helping photographers and cameramen. In addition, photometers are used to determine the level of safe illumination in other areas, for example, in crop production, in museums, where it is necessary to maintain the required illumination.

Safe flow of light at work

Working in a dark or dimly lit room can cause various health problems, be it blurred vision, depression or other physiological and psychological disorders. For this reason, in the workplace, as part of occupational safety regulations, minimum safe lighting requirements are included. The final measurement result produced by the photometer includes the area of ​​light propagation. These indicators ensure sufficient illumination of the entire room.

Light flux and museum exhibits

The speed with which the museum exhibits will deteriorate and fade depends on the illumination and the intensity of the flow from the light source. Museum workers are working to determine the illumination of exhibits. This is done in order to ensure that there is a safe amount of luminous flux on museum units, as well as to ensure a sufficient level of illumination for visitors while viewing the exhibit.

The illumination level can be measured with a photometer, which is not easy to do because it should be installed as close to the exhibit as possible, and this requires removing the protective glass, turning off the alarm and obtaining permission. This task is made easier in another way, which is often used by museum staff. Instead of a photometer, a camera is used, which is not a replacement for a photometer in situations where more accurate measurements of the found lighting problem are required, but it is quite enough to identify a deviation from the norm.

You can determine the exposure with your camera based on the light level readings. The exposure illumination level is easy to determine using simple calculations. Museum staff resort to a formula or use a table, where exposure is represented in illuminance units. When making calculations, do not forget that the camera absorbs a certain amount of light, so you should take this into account.

Before providing a plant with the light it needs for photosynthesis, you need to know how much each crop needs. Gardeners and plant growers know this. They measure light levels to make sure each plant gets the amount of light it needs. Photometers are often used for such procedures.

Photometers are also widely used in laboratory practice. For example, a spectrum of samples is determined, with the help of which the chemical composition is established. A special class of such devices includes a flame photometer. He detects alkali metals in samples, such as sodium, lithium, potassium. To detect them, you need to burn the sample at a high temperature and use a photometer to analyze the spectrum of the flame. This problem is much more difficult to solve in other ways.

Modern photometers convert light radiation into electrical impulses; they are recorded using the principle of an ammeter and voltmeter, and then converted into a computer format.

A photometer is an instrument covering many fields of knowledge, such as chemistry, molecular biology, physics, materials science and others. The photometer is widely used in industry, laser and optical products. In addition to the chemical laboratory, the photometer finds application in forensic laboratories.

Thus, from the above you have learned about the units of measurement of light, which It is better to buy lamps with the specified number of lumens that the concepts of illumination and brightness differ, and the amount of light can be measured with a special device.

In Soviet times, when choosing a light bulb, consumers were guided by the number of watts in it. The more of them, the brighter the device shone. However, today (when many new varieties of lamps have appeared on store shelves) we are increasingly faced with such a concept as “lumen”. What is it, how does it differ from a watt, and what is the unit called lumen per watt? Let's find answers to these questions.

What is "lumen"

In the middle of the twentieth century. To avoid confusion in units of measurement between different countries, the universal SI system was introduced. It is thanks to her that we have watts, amperes, meters, kilograms, etc.

According to it, (visible electromagnetic radiation) is In fact, these units measure the amount of light emanating from its source.

Also, to the question of what “lumen” is, you can answer that this is the name of a famous Russian rock band from Ufa. Having started its activities in 1998, it has continued to be loved by many listeners in the Russian Federation and abroad for almost twenty years.

Origin of the word

Having learned what a lumen is, it is worth clarifying where this word came from in the Russian language.

Like most SI unit names, the term in question is a Latinism. It is derived from the word “light” (lūmen).

At the same time, some linguists argue that the noun could be formed from the Proto-Indo-European word leuk (white) or from lucmen (the meaning is not precisely established).

What is the difference between lumen and lux

Considering the meaning of the word “lumen”, it is worth mentioning such a close concept as “lux”.

Both of these terms refer to light energy units, but lumen is the entire light emitted by a source, and lux is the amount of light that reached the illuminated surface and was not stopped by some obstacles to form shadows.

The interdependence of these units can be reflected with the following formula: 1 lux = 1 lumen/1 square meter.

For example, if a lamp illuminating an area measuring 1 m 2 emits 50 lumens, then the illumination of this place is equal to 50 lux (50 lm / 1 m 2 = 50 lux).

However, if the same lamp with the same amount of light is used for a room of 10 m2, then the illumination in it will be less than in the previous case. A total of 5 lux (50lm/10m2 = 5 lux).

In addition, such calculations did not take into account the presence of various obstacles that prevent light rays from reaching the surface, which significantly reduces the level of illumination.

Due to this situation, in every country in the world there are lighting standards for various buildings. If it is lower than them, a person’s vision does not receive enough light and deteriorates. For this reason, when planning to make repairs or rearrangements in your home, it is always important to take this nuance into account.

There are also a number of design programs in which such calculations are made automatically.

Lumen and Watt

Having learned the difference and meaning of lumen and lux, it is worth paying attention to another SI unit - the watt.

Because they are used for light bulbs, some believe that these units can be freely related to each other. However, this is not quite true.

The fact is that the power of energy that a light bulb consumes is measured in watts, and the amount of light that it emits is measured in lumens.

In the days when only incandescent lamps existed, it was easier to calculate the amount of light from such a device. Since a 100 W bulb produced about 1600 lumens of light. While a similar 60 W device produces 800 lm. It turned out that the more energy consumed, the better the lighting.

But today everything is different. In recent decades, several new types of lighting sources have been invented (fluorescent, etc.). Their advantage is cost-effectiveness. That is, they shine brighter with less energy used.

In this regard, if it is necessary to create a relationship between watts and lumens, you need to take into account the type of lamp and look for its aperture in special tables.

It is worth noting that an ordinary person sometimes does not want to rebuild and understand all these subtleties. Therefore, most domestic manufacturers of new types of light bulbs indicate on the labels not only the number of lumens, but how much less watts the device consumes (compared to an incandescent lamp). For example: a 12-watt lamp produces the same light as 75 watts.

Unit of measurement “lumen per watt”: its meaning and scope of application

For example, a classic 40 W incandescent lamp has a light output of 10.4 lm/W. At the same time, for an induction lamp with the same power this figure is much higher - 90 lm/W.

For this reason, when choosing a lighting device for your home, you should not be lazy, but find out the level of its light output. As a rule, such data is on the labels.

Lumen (lm, lm)- unit of measurement of luminous flux in SI. Where SI is the system of units of physical quantities (French: Le Syst?me International d'Unit?s, SI).

One lumen is equal to the luminous flux emitted by a point isotropic source with a luminous intensity equal to one candela into a solid angle of one steradian (1 lm = 1 cd? sr). The total luminous flux created by an isotropic source with a luminous intensity of one candela is equal to 4? lumens.

A typical 100 W incandescent lamp produces a luminous flux of approximately 1300 lm. A 26 W compact fluorescent fluorescent lamp produces a luminous flux of approximately 1600 lm. The luminous flux of the Sun is 3.63·10 to the 28th power of lm.

Lumen is the total luminous flux from a source. However, this measurement usually does not take into account the focusing efficiency of the reflector or lens and is therefore not a direct parameter for assessing the brightness or useful performance of the beam. A wide beam of light can have the same lumens as a narrowly focused beam. Lumens cannot be used to determine beam intensity because the lumen rating includes all scattered wasted light.

Lux (lx)- unit of measurement of illumination in the SI system.

Lux is equal to the illumination of a surface with an area of ​​1 sq. m when the luminous flux of radiation incident on it is equal to 1 lumen.

100 lumens were collected and projected onto a 1-meter square area. The illumination of the area will be 100 lux. The same 100 lumens aimed at 10 square meters will produce 10 lux of illumination.

Candela (cd, cd)- one of the seven basic units of measurement of the SI system, equal to the intensity of light emitted in a given direction by a source of monochromatic radiation with a frequency of 540·10 to the 12th power of Hz, the energy intensity of which in this direction is (1/683) W/sr. Steradian (Russian designation: ср, international: sr) is a unit of measurement of solid angles.

The selected frequency corresponds to the color green. The human eye is most sensitive in this region of the spectrum. If the radiation has a different frequency, then greater energy intensity is required to achieve the same luminous intensity.

Previously, candela was defined as the intensity of light emitted by a black body perpendicular to a surface with an area of ​​1/60 sq. cm at the melting point of platinum (2042.5 K). In the modern definition, the coefficient of 1/683 is chosen so that the new definition matches the old one.

The intensity of light emitted by a candle is approximately equal to one candela (Latin candela - candle), so this unit of measurement was previously called a “candle”, now this name is outdated and is not used.

Luminous intensity of typical sources:

Black Diamond is a trendsetter in the world of professional mountaineering and climbing equipment. The brand produces high-quality headlamps and pendant lamps that can be used even at a depth of one meter underwater for half an hour. BD offers travel lighting with up to 200 lumens of light output and a relatively light weight. Many flashlights are equipped with several lighting modes for ease of use on the mountaineering route and at home. Bright, light, neat and practical, BlackDiamond flashlights will not let you down even in the most extreme situations.

Luminous flux of lamps (lm)

big LED-high, big LED-med, big LED-low, 5 MM - High, 5 MM - medium, 5 MM - low

Light flow- the power of light radiation, i.e. visible radiation, assessed by the light sensation that it produces on the human eye. Luminous flux is measured in lumens.

For example, an incandescent lamp (100 W) emits a luminous flux of 1350 lm, and a fluorescent lamp LB40 - 3200.

One lumen equal to the luminous flux emitted by a point isotropic source, with a luminous intensity equal to one candela, per solid angle, equal to one steradian (1 lm = 1 cd sr).

The total luminous flux created by an isotropic source with a luminous intensity of one candela is equal to 4π lumens.

There is another definition: the unit of luminous flux is lumen(lm), equal to the flux emitted by an absolutely black body from an area of ​​0.5305 mm 2 at the solidification temperature of platinum (1773 ° C), or 1 candle · 1 steradian.

The power of light- spatial density of the luminous flux, equal to the ratio of the luminous flux to the value of the solid angle in which the radiation is uniformly distributed. The unit of luminous intensity is the candela.

Illumination- surface density of the light flux incident on the surface, equal to the ratio of the light flux to the size of the illuminated surface over which it is evenly distributed.

The unit of illumination is lux (lx), equal to the illumination created by a luminous flux of 1 lm, uniformly distributed over an area of ​​1 m2, i.e. equal to 1 lm/1 m2.

Brightness- surface density of luminous intensity in a given direction, equal to the ratio of luminous intensity to the area of ​​projection of the luminous surface onto a plane perpendicular to the same direction.

The unit of brightness is candela per square meter (cd/m2).

Luminosity (luminosity)- surface density of the luminous flux emitted by the surface, equal to the ratio of the luminous flux to the area of ​​the luminous surface.

The unit of luminosity is 1 lm/m2.

Units of light quantities in the international system of units SI (SI)

Examples:

ELECTROTECHNICAL HANDBOOK"
Under the general editorship. MPEI professors V.G. Gerasimova and others.
M.: MPEI Publishing House, 1998

How to choose the right LED lamp.

What is written on the boxes, what do certain parameters mean.

LED (“Light Emitting Diode”) means LED.

In order to decide on the choice of lamp.

The most important indicator of a lamp is

Light flow is the amount of visible light.

Designated Lm (lumen). In order to understand a lot or a little.

It is enough to know that the usual a 60 watt incandescent lamp is approximately 660 lm.

A 100 watt lamp is 1140 lm.

Indicated in watts (W) - this is how much electricity is consumed (“how much the meter turns up”). A more powerful lamp does not mean brighter.

An energy-saving lamp is determined precisely by the ratio of these 2 parameters - getting as much light Lm as possible and spending as little electricity W as possible on it. Our LED lamps are approximately 85-115 lm/W.

Voltage.

Designated V (volt), as a rule, lamps operate on 220 volts, or 12V (via a step-down transformer or automobile), even less often they operate on 24-36v (ships and industrial premises with high humidity). On the box they write the limits from and to (how sensitive the lamp is to voltage changes). LED lamps operate in the range from 100 to 240v.

Temperature of light.

Designated K (Kelvin) how “warm” or “cold” the light from the lamp is.

It has nothing to do with the physical heating of the lamp! Varies depending on the number of watts only for lamps with incandescent filament.

A slightly crafty indicator that has an exact measurement. Different lamps with the same indicator may differ in shades of light.

In energy saving and LED lamps this indicator is achieved by adding one or another phosphor during production

Many people, when buying a lamp, do not pay attention to this indicator, and after installing the lamp they are dissatisfied with the fact that “The light is somehow ghostly or cold” or, conversely, that it is too “yellow”.

To prevent this from happening and to ensure that your expectations are not mistaken, we present the table below

The lower the indicator, the warmer the light, the higher the colder.

From household examples, an incandescent lamp 60 watts has an indicator of 2700K

Daylight in cloudy weather - 6500-7000 K.

Lamps generally have indicators

2700K(warm white)

4100K(neutral white)

6500K(cold)

7500 (white daylight).

Warm light - more homely and cozy, for comfort and relaxation. Lamps with warm light are installed in bedrooms and living rooms.

Neutral and cold light is more effective and puts you in a working mood; it more clearly shows objects as they are. Lamps with neutral and cold light are installed to illuminate work areas, offices, dressing rooms, and hobby rooms.

Neutral and cool blue radiation in itself can affect a person’s biological clock, so for indoor lighting you should choose high-quality lamps with a color temperature of 4000K-6500K, which corresponds to natural daylight.

Types of lamp bases

Color rendering index.

Denoted Ra (aka CRI).

This is an indicator of how accurately the shades of illuminated objects are conveyed.

Ra 0 - everything is in black and white.

This indicator determines how correctly colors will be perceived in a given light. For example, light sources with Ra>95 are required for museums and art galleries; light sources with Ra>90 are suitable for clothing stores and boutiques. For home, it is recommended to choose lamps and luminaires with a color rendering index value of at least Ra80

Lower values ​​are allowed for lighting, utility and utility rooms, roads, courtyards in areas where the quality of light is not important, but energy saving is the main thing.

Our LED lamps have 80 - 92 Ra

Luminous flux angle.

It happens 20, 35. The most common for spotlights is 120 degrees.

With the same luminous flux, completely different lighting effects.

For accent light (if you need to illuminate something specifically), it is better to choose a lamp with a small angle.

For general lighting (ceiling), it is better to choose a lamp with a wide angle, such as 120 degrees.

There is detailed information about spotlights on ceilings

Heatsink in LED lamps:

Any LED lamp must have a heat sink.

In our understanding, LED lamps do not heat up, however For LEDs, their own heat is destructive. This is what the radiator is made for.

The better and larger the radiator, the longer the LED lamp will last.

Unfortunately, at the moment it is impossible to produce an LED lamp that is both powerful, small and durable. (One of the parameters will decrease at the expense of the others). The more powerful the LED lamp, the larger it is(if we are talking about high-quality LED lamps)

Some low-quality manufacturers, in order to reduce the cost of their products at any cost, reduce the radiator, according to the principle “it will last a year, but oh well.”

Most buyers choose LED lamps based on two criteria: power/price, which is fundamentally wrong, since more power does not mean more light.

High-quality radiator - aluminum with the addition of silver and copper, is a guarantee for a long service life without reducing the luminous flux over time.

Ripple in LED lamps. not visible to the naked eye

In high-quality LED lamps, pulsation is absent or minimal.

Manufacturers of quality lamps indicate, for example:

• No pulsation
• 0% ripple factor.

This is a very important indicator. Since pulsation negatively affects vision and fatigue, especially when working with moving objects or when reading. It can cause headaches, pain in the eyes, and so on, depending on the degree of pulsation and the time spent in such lighting.

This effect is difficult to notice with the naked eye. The lamp flickers so often that the eye (pulsation) does not see it, but it puts a strain on the brain and vision.

The easiest way to determine whether an LED lamp has pulsation is to point your smartphone camera at it.

You will get something like this picture with moving stripes.

This is typical for cheap and not very high-quality lamps, whose manufacturers do not indicate this indicator on the packaging and are silent. This is due to the incorrect design of the driver, which produces not a constant, but a pulsating current.

Such lamps are not suitable for basic home and work lighting.

But they can be used for additional, non-primary lighting: lighting of storage rooms, attics, basements, some street lamps, duty lamps.

Or for local lighting: lighting for pictures, in the refrigerator, etc.

But you definitely don’t need to install such lamps in chandeliers, sconces (especially for reading), or work lamps.

It is strictly forbidden to use lamps with a high degree of pulsation when working with moving mechanisms and machines. The rotation speed may coincide with the flickering frequency and the mechanism will appear to be motionless, which may result in serious injury.

ONLY transparent lamps (incandescent or LED) are used in crystal lamps; in order for the crystal to “play” and break the light, a point source of light is needed (sun, candle, tungsten filament, open LED).

This is essentially an ordinary incandescent lamp, they come in different shapes.

Due to the increased length of the tungsten filament, it looks more impressive. They are often placed in loft-style lamps.

The bulb has a yellowish tint, so the light is warmer than that of an ordinary incandescent lamp 2100-2400K. This lamp will last about 2 years.

These lamps are suitable for additional lighting, creating a more comfortable atmosphere. It is not advisable to use it for main and task lighting.

Buy LED lamps cheap?

Cheap LED lamps exist on the market, but, as a rule, these are low-efficiency lamps whose power consumption is higher and whose luminous flux is low, or their design allows the manufacturer not to spend significant funds on the driver and cooling radiator.

High-quality lamps or complex decorative LED products cannot have a low price. A low price may be due to raw materials of dubious quality. LED lamps from well-known brands are often counterfeited and can be sold below the average market price, although more often they try to keep prices at an appropriate level to obtain excess profits. Low quality LED lamps can cause serious harm to health and vision. They contain toxic materials that often have a distinct chemical odor when the lamp heats up during operation. The light from LED counterfeits does not correspond to the declared color temperature and power. Diffusers on cheap lamps perform a purely aesthetic function; therefore, they cannot protect the eyes from too bright radiation and can cause a burn to the retina. High-quality LEDs do not have infrared or ultraviolet healing in their spectrum.

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